Ceramic coatings are applied to gas turbine engine hardware, such as turbine blades and vanes, to provide thermal protection against the high temperatures of the turbine engine. For example, so called thermal barrier coatings are applied to gas turbine engine blade and vane components by first depositing a bondcoat on the component followed by depositing a ceramic layer on the bondcoat by electron beam physical vapor deposition. In the electron beam physical vapor deposition of the ceramic layer, a source of the ceramic material, such as yttria stabilized zirconia, is heated by impinging an electron beam thereon to evaporate the ceramic material for deposition on the components, which are positioned in the ceramic vapor cloud to this end.
The electron beam physical vapor deposition of the ceramic layer on the turbine components is conducted in a stainless steel or other coating box or enclosure, which may be water cooled. It has been discovered by applicants that during the course of coating with the evaporated ceramic material, the ceramic coating material inadvertently collects on the inside walls of the relatively cool coating box or enclosure in addition to depositing on the components to be coated. The collected ceramic material has been found to act as thermal insulation on the inside enclosure walls to an extent that excess heat can build up in the coating box or enclosure exceeding the preselected desired coating temperature for the particular components to be coated, resulting in defective or unacceptable coated components.
It is an object of the present invention to provide method and apparatus that overcome the aforementioned problem and provide control of coating temperature during vapor deposition in a coating box or enclosure.